//! PostgreSQL协议支持
//! 
//! 实现PostgreSQL wire protocol兼容性

use crate::{Error, Result};

/// PostgreSQL协议处理器
#[derive(Debug)]
pub struct PostgresProtocolHandler {
    /// 连接状态
    state: ConnectionState,
    /// 协议统计信息
    stats: PostgresStats,
}

/// PostgreSQL协议统计信息
#[derive(Debug, Clone, Default)]
pub struct PostgresStats {
    /// 总消息数
    pub total_messages: u64,
    /// 查询消息数
    pub query_messages: u64,
    /// 错误消息数
    pub error_messages: u64,
    /// 连接数
    pub connections: u64,
}

impl PostgresProtocolHandler {
    /// 创建新的协议处理器
    pub fn new() -> Self {
        Self {
            state: ConnectionState::Startup,
            stats: PostgresStats::default(),
        }
    }

    /// 获取统计信息
    pub fn get_stats(&self) -> &PostgresStats {
        &self.stats
    }

    /// 重置统计信息
    pub fn reset_stats(&mut self) {
        self.stats = PostgresStats::default();
    }
    
    /// 处理客户端消息
    pub async fn handle_message(&mut self, message: &[u8]) -> Result<Vec<u8>> {
        // 更新统计信息
        self.stats.total_messages += 1;

        // 简化实现，实际需要解析PostgreSQL协议消息
        tracing::debug!("处理PostgreSQL消息，长度: {}", message.len());

        let result = match self.state {
            ConnectionState::Startup => {
                self.handle_startup_message(message).await
            }
            ConnectionState::Ready => {
                self.stats.query_messages += 1;
                self.handle_query_message(message).await
            }
            ConnectionState::InTransaction => {
                self.handle_transaction_message(message).await
            }
        };

        // 如果处理失败，更新错误统计
        if result.is_err() {
            self.stats.error_messages += 1;
        }

        result
    }
    
    /// 处理启动消息
    async fn handle_startup_message(&mut self, _message: &[u8]) -> Result<Vec<u8>> {
        self.state = ConnectionState::Ready;
        
        // 返回认证成功消息
        Ok(b"Authentication successful".to_vec())
    }
    
    /// 处理查询消息
    async fn handle_query_message(&mut self, _message: &[u8]) -> Result<Vec<u8>> {
        // 简化实现，返回查询结果
        Ok(b"Query result".to_vec())
    }
    
    /// 处理事务消息
    async fn handle_transaction_message(&mut self, _message: &[u8]) -> Result<Vec<u8>> {
        // 简化实现
        Ok(b"Transaction message handled".to_vec())
    }
}

impl Default for PostgresProtocolHandler {
    fn default() -> Self {
        Self::new()
    }
}

/// 连接状态
#[derive(Debug, Clone, PartialEq)]
enum ConnectionState {
    Startup,
    Ready,
    InTransaction,
}

/// PostgreSQL消息类型
#[derive(Debug, Clone)]
pub enum PostgresMessage {
    /// 查询消息
    Query(String),
    /// 准备语句
    Parse {
        statement_name: String,
        query: String,
        parameter_types: Vec<i32>,
    },
    /// 绑定参数
    Bind {
        portal_name: String,
        statement_name: String,
        parameters: Vec<Vec<u8>>,
    },
    /// 执行
    Execute {
        portal_name: String,
        max_rows: i32,
    },
    /// 同步
    Sync,
    /// 终止
    Terminate,
}

/// PostgreSQL响应消息
#[derive(Debug, Clone)]
pub enum PostgresResponse {
    /// 认证成功
    AuthenticationOk,
    /// 就绪状态
    ReadyForQuery(char),
    /// 行描述
    RowDescription(Vec<FieldDescription>),
    /// 数据行
    DataRow(Vec<Option<Vec<u8>>>),
    /// 命令完成
    CommandComplete(String),
    /// 错误响应
    ErrorResponse(String),
}

/// 字段描述
#[derive(Debug, Clone)]
pub struct FieldDescription {
    /// 字段名
    pub name: String,
    /// 表OID
    pub table_oid: i32,
    /// 列属性号
    pub column_attribute_number: i16,
    /// 数据类型OID
    pub data_type_oid: i32,
    /// 数据类型大小
    pub data_type_size: i16,
    /// 类型修饰符
    pub type_modifier: i32,
    /// 格式代码
    pub format_code: i16,
}

/// PostgreSQL服务器
#[derive(Debug)]
pub struct PostgresServer {
    /// 监听地址
    bind_address: String,
    /// 监听端口
    port: u16,
}

impl PostgresServer {
    /// 创建新的PostgreSQL服务器
    pub fn new(bind_address: String, port: u16) -> Self {
        Self {
            bind_address,
            port,
        }
    }
    
    /// 启动服务器
    pub async fn start(&self) -> Result<()> {
        tracing::info!("启动PostgreSQL服务器 {}:{}", self.bind_address, self.port);
        
        // 简化实现，实际需要监听TCP连接
        // let listener = TcpListener::bind(format!("{}:{}", self.bind_address, self.port)).await?;
        
        Ok(())
    }
    
    /// 停止服务器
    pub async fn stop(&self) -> Result<()> {
        tracing::info!("停止PostgreSQL服务器");
        Ok(())
    }
    
    /// 处理客户端连接
    async fn handle_connection(&self, _stream: tokio::net::TcpStream) -> Result<()> {
        let mut handler = PostgresProtocolHandler::new();
        
        // 简化实现，实际需要读取和写入TCP流
        loop {
            // 读取消息
            let message = vec![]; // 从stream读取
            
            // 处理消息
            let response = handler.handle_message(&message).await?;
            
            // 发送响应
            // stream.write_all(&response).await?;
            
            break; // 简化实现，只处理一次
        }
        
        Ok(())
    }
}

/// PostgreSQL数据类型OID常量
pub mod pg_types {
    pub const BOOL: i32 = 16;
    pub const BYTEA: i32 = 17;
    pub const CHAR: i32 = 18;
    pub const NAME: i32 = 19;
    pub const INT8: i32 = 20;
    pub const INT2: i32 = 21;
    pub const INT2VECTOR: i32 = 22;
    pub const INT4: i32 = 23;
    pub const REGPROC: i32 = 24;
    pub const TEXT: i32 = 25;
    pub const OID: i32 = 26;
    pub const TID: i32 = 27;
    pub const XID: i32 = 28;
    pub const CID: i32 = 29;
    pub const OIDVECTOR: i32 = 30;
    pub const JSON: i32 = 114;
    pub const XML: i32 = 142;
    pub const PGNODETREE: i32 = 194;
    pub const POINT: i32 = 600;
    pub const LSEG: i32 = 601;
    pub const PATH: i32 = 602;
    pub const BOX: i32 = 603;
    pub const POLYGON: i32 = 604;
    pub const LINE: i32 = 628;
    pub const FLOAT4: i32 = 700;
    pub const FLOAT8: i32 = 701;
    pub const ABSTIME: i32 = 702;
    pub const RELTIME: i32 = 703;
    pub const TINTERVAL: i32 = 704;
    pub const UNKNOWN: i32 = 705;
    pub const CIRCLE: i32 = 718;
    pub const CASH: i32 = 790;
    pub const MACADDR: i32 = 829;
    pub const INET: i32 = 869;
    pub const CIDR: i32 = 650;
    pub const MACADDR8: i32 = 774;
    pub const ACLITEM: i32 = 1033;
    pub const BPCHAR: i32 = 1042;
    pub const VARCHAR: i32 = 1043;
    pub const DATE: i32 = 1082;
    pub const TIME: i32 = 1083;
    pub const TIMESTAMP: i32 = 1114;
    pub const TIMESTAMPTZ: i32 = 1184;
    pub const INTERVAL: i32 = 1186;
    pub const TIMETZ: i32 = 1266;
    pub const BIT: i32 = 1560;
    pub const VARBIT: i32 = 1562;
    pub const NUMERIC: i32 = 1700;
    pub const REFCURSOR: i32 = 1790;
    pub const REGPROCEDURE: i32 = 2202;
    pub const REGOPER: i32 = 2203;
    pub const REGOPERATOR: i32 = 2204;
    pub const REGCLASS: i32 = 2205;
    pub const REGTYPE: i32 = 2206;
    pub const REGROLE: i32 = 4096;
    pub const REGNAMESPACE: i32 = 4089;
    pub const UUID: i32 = 2950;
    pub const LQUERY: i32 = 3615;
    pub const LTREE: i32 = 3614;
    pub const LTXTQUERY: i32 = 3616;
    pub const JSONB: i32 = 3802;
    pub const JSONPATH: i32 = 4072;
    pub const TXID_SNAPSHOT: i32 = 2970;
    pub const PG_SNAPSHOT: i32 = 5038;
    pub const INT4RANGE: i32 = 3904;
    pub const NUMRANGE: i32 = 3906;
    pub const TSRANGE: i32 = 3908;
    pub const TSTZRANGE: i32 = 3910;
    pub const DATERANGE: i32 = 3912;
    pub const INT8RANGE: i32 = 3926;
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_postgres_handler_creation() {
        let handler = PostgresProtocolHandler::new();
        assert_eq!(handler.state, ConnectionState::Startup);
    }
    
    #[tokio::test]
    async fn test_startup_message_handling() {
        let mut handler = PostgresProtocolHandler::new();
        let message = b"startup message";
        
        let response = handler.handle_message(message).await.unwrap();
        assert!(!response.is_empty());
        assert_eq!(handler.state, ConnectionState::Ready);
    }
    
    #[test]
    fn test_postgres_server_creation() {
        let server = PostgresServer::new("127.0.0.1".to_string(), 5432);
        assert_eq!(server.bind_address, "127.0.0.1");
        assert_eq!(server.port, 5432);
    }
    
    #[test]
    fn test_field_description() {
        let field = FieldDescription {
            name: "id".to_string(),
            table_oid: 1,
            column_attribute_number: 1,
            data_type_oid: pg_types::INT4,
            data_type_size: 4,
            type_modifier: -1,
            format_code: 0,
        };
        
        assert_eq!(field.name, "id");
        assert_eq!(field.data_type_oid, pg_types::INT4);
    }

    #[tokio::test]
    async fn test_postgres_stats() {
        let mut handler = PostgresProtocolHandler::new();

        // 初始统计信息
        let stats = handler.get_stats();
        assert_eq!(stats.total_messages, 0);
        assert_eq!(stats.query_messages, 0);
        assert_eq!(stats.error_messages, 0);

        // 处理启动消息
        let startup_message = b"startup";
        handler.handle_message(startup_message).await.unwrap();

        let stats = handler.get_stats();
        assert_eq!(stats.total_messages, 1);

        // 处理查询消息
        let query_message = b"SELECT 1";
        handler.handle_message(query_message).await.unwrap();

        let stats = handler.get_stats();
        assert_eq!(stats.total_messages, 2);
        assert_eq!(stats.query_messages, 1);

        // 重置统计信息
        handler.reset_stats();
        let stats = handler.get_stats();
        assert_eq!(stats.total_messages, 0);
        assert_eq!(stats.query_messages, 0);
    }

    #[test]
    fn test_postgres_protocol_handler_creation() {
        let handler = PostgresProtocolHandler::new();
        assert_eq!(handler.state, ConnectionState::Startup);
        assert_eq!(handler.get_stats().total_messages, 0);
    }
}
